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/* Copyright 2006-2008 Joaquin M Lopez Munoz.
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*
* See http://www.boost.org/libs/flyweight for library home page.
*/
#ifndef BOOST_FLYWEIGHT_TRACKING_TAG_HPP
#define BOOST_FLYWEIGHT_TRACKING_TAG_HPP
#if defined(_MSC_VER)&&(_MSC_VER>=1200)
#pragma once
#endif
#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
#include <boost/parameter/parameters.hpp>
#include <boost/type_traits/is_base_and_derived.hpp>
namespace boost{
namespace flyweights{
/* Three ways to indicate that a given class T is a tracking policy:
* 1. Make it derived from tracking_marker.
* 2. Specialize is_tracking to evaluate to boost::mpl::true_.
* 3. Pass it as tracking<T> when defining a flyweight type.
*/
struct tracking_marker{};
template<typename T>
struct is_tracking:is_base_and_derived<tracking_marker,T>
{};
template<typename T=parameter::void_>
struct tracking:parameter::template_keyword<tracking<>,T>
{};
} /* namespace flyweights */
} /* namespace boost */
#endif
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